The present invention relates to railroad freight cars, and in particular to stiffened bulkheads between hoppers of a covered hopper car.
Covered hopper railroad cars for carrying bulk cargo such as grain, sand, fertilizer, woodchips, and the like may have two or more hoppers located adjacent one another along the length of a hopper car. Such a hopper car typically has a slope sheet at each end of the car and additional slope sheets leading to the outlets at the bottoms of the several hoppers. Vertical transverse bulkheads usually of sheet metal, separate adjacent ones of the hoppers and extend from the top of the car down to the upper end of a slope sheet of each one of a pair of the hoppers separated by the bulkheads.
A hatch is typically provided in the roof of the car at the top of each hopper so that cargo can be loaded into the hopper, and to facilitate washing the interior of a hopper after emptying the car and before loading the car with a different type of cargo. Some types of cargo, such as some types of plastic resins, may be granular, in pellet form, or even of a finely divided flour-like particulate composition, and may not readily flow out from a hopper when unloading a car.
In order to assure that a hopper is readily emptied and that the entire surface of a bulkhead between hoppers can be washed clean by spraying from the topside hatch, some prior bulkheads have been a single planar piece. Such a large flat expanse of sheet metal, however, is subjected to various forces during loading, unloading, and travel of the hopper car, with the result that cracking too often occurs around the perimeter of such a planar bulkhead. A low natural resonant frequency of such a planar bulkhead can result in failure of the bulkhead, caused by vibration when a car travels empty.
In order to stiffen a bulkhead without adding excessive weight to the railcar, it has been known to bend the sheet material of a bulkhead along parallel horizontal lines to form a stiffener that may resemble a channel beam extending transversely along the bulkhead. Typically two such stiffeners have been incorporated in a bulkhead, each having sloping top and bottom portions joined by a vertical portion that is offset, in a longitudinal direction with respect to the car body, from a vertical main plane of the bulkhead. Each stiffener thus may have a trapezoidal profile and typically extends the full width of the car body. Such stiffeners reduce the ability of the bulkhead to flex and thus tend to reduce cracking at the margins of the bulkhead, but the stiffeners add to the weight of a car and may have other problems.
Because of the shape and desired locations of such prior art stiffeners, some granular and particulate cargo materials, especially non-slippery cargo materials having a low density, tend to accumulate and remain atop a stiffener of the type just described, so that the hopper does not empty itself completely. Additionally, it has been impossible to wash the underside of a lower stiffener of such a design satisfactorily with a spray directed from a topside hatch of a hopper including such a stiffened bulkhead.
What is desired, then, is a covered hopper car including adequately stiffened, yet not excessively heavy, bulkheads between adjacent hoppers. It is also desired for such stiffeners to promote flow of all of a granular or particulate cargo from a hopper. It is also desired for the stiffened bulkhead in such a covered hopper car to have all of its surfaces available to be washed effectively by a spray directed from a topside hatch opening of a hopper including such a bulkhead.